Brachytherapy is implanted radioactive sources usually in the form of seeds. They are placed in or just next to a tumor. They can be left in place permanently or only temporarily, depending on the type of cancer. In order to accurately place the sources, special catheters or applicators are utilized.

There are two types of brachytherapy:
Intracavity treatment & Interstitial treatment

With intracavity treatment the radioactive sources are put into a location close to the tumor, for example the cervix, the vagina or the windpipe.

With interstitial treatment the radioactive sources are placed directly in the cancerous tissues, such as the prostate. The sources used are either iodine or palladium. For the prostate they are inserted into the prostate via needles that enter through the skin behind the testicles. As with external beam treatments, an accurate and precise mapping is done with regard to the placement of seeds to direct the radiation to the tumor and spare the normal tissues. The seeds will give off radiation over the next couple months to year until the radioactive material is gone from the seeds. They are harmless at this point so they are just left in place. These procedures typically require a brief hospitalization and anesthesia. The patients may have a few restrictions with permanent implants, but then can quickly return to their normal activities.

Patients who receive the intracavity temporary implants are required to stay in a private room in the hospital for the planned amount of time for the radiation to expose the tumor.
The main advantages to prostate brachytherapy are:

It is an outpatient procedure in which the patient can generally resume normal daily activities quickly

It can be done alone or together with External Beam IMRT/IGRT.
The seeds are implanted in the prostate and minimize the amount of radiation to the normal surrounding structures. This also allows for a potentially higher dose of radiation to the prostate.

The following image is an x-ray of the pelvis after the seeds have been implanted.